Stem cells have unique abilities to renew their own population through cell division, or differentiate into other cell types. These abilities give stem cells enormous potential for regenerating tissues and repairing damaged or diseased cell populations. One essential step to unlocking this potential is inducing the stem cells to differentiate into desired cell types in vitro. Thus, controlling differentiation of stem cells in vitro is an area of ongoing study. Another key step is identifying the differentiated cells of a specific type, a task often performed by removing cells from the culture and immunostaining for cell-specific protein markers. For monitoring growth and differentiation of stem cells in real time, it would be useful to have a non-invasive method for identifying differentiating cells as they progress through the stages of differentiation. A non-invasive platform would also allow monitoring while adding or removing factors that modulate stem cell differentiation.
Two lineages of particular interest are the trophectoderm lineage and the neurectoderm lineage. Trophectoderm (TE) refers to a layer of cells that form on the outer layer of a blastocyst, and later differentiates to form extra-embryonic tissue such as the placenta. The timing of TE differentiation is critical because successful implantation of an embryo requires synchrony between the developing placenta and uterine receptivity. Neurectoderm (NE) refers to the ectoderm which differentiates to form cells and structures of the nervous system. All of the specialized cells in the nervous system are derived from NE, so it would be useful to establish methods for directing differentiation into NE and other specialized cell types. However, factors controlling the development of TE are not well-understood. Accordingly, there remains a need for in vitro protocols for inducing differentiation of stem cells into TE, NE, or cells derived from these lineages, and for identifying the differentiation of these cell types in a non-invasive manner.